1. Field of the Invention
The present invention relates to a technique for inspecting nozzles for abnormalities in an inkjet printing apparatus.
2. Description of the Background Art
Inkjet printing apparatuses are conventionally known. An inkjet printing apparatus includes a plurality of nozzles for ejecting ink, and records an image on printing paper by ejecting ink from each of the nozzles toward the printing paper while moving the nozzles and the printing paper relative to each other. Such inkjet printing apparatuses are widely used in the step of printing because of their relatively low running costs.
Since the inkjet printing apparatus ejects ink from the plurality of nozzles as mentioned above, the quality of images recorded by the inkjet printing apparatus deteriorates if an abnormality occurs in some of the nozzles. The quality of the recorded images deteriorates, for example, if ink is no longer ejected from some of the nozzles, a line printed by the ink ejected from some of the nozzles has a reduced width, or the ink ejected from some of the nozzles is not placed in proper positions.
Such nozzle abnormalities result from the entry of air into the nozzles, the deposition of dust onto the nozzles, and other factors. It has hence been difficult to automatically detect the nozzle abnormalities by effecting electrical control of the interior of the printing apparatus. For this reason, whether there is a nozzle abnormality or not has been judged by a user that views a predetermined test pattern printed on printing paper by the eyes.
However, viewing the printed test pattern by the eyes becomes an enormous burden on the user. In particular, it takes a considerable amount of time for an unskilled user to perform this viewing operation. Depending on the color of the ink ejected from the nozzles, there are cases in which viewing the test pattern by the eyes is difficult. In such cases, it has been difficult to reliably inspect the nozzles for abnormalities.